1 B 2 state of SO 2 G Barratt Park Jun Jiang and Robert Field The C 1 B 2 state of SO 2 has a doubleminimum potential in n 3 J B Coon N W Naugle ID: 631439
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Slide1
The origin of unequal bond lengths in the C̃1B2 state of SO2
G. Barratt Park,
Jun Jiang
, and Robert FieldSlide2
The C̃ 1B
2
state of SO2 has a double-minimum potential in n3
J. B. Coon, N. W.
Naugle
, and R. D. McKenzie,
J. Mol.
Spectr
.
20
, 107 (1966).
J
. C. D. Brand, P. H. Chiu, A. R. Hoy,
J. Mol.
Spectr
.
60
, 43 (1976).
A. R. Hoy, J. C. D. Brand,
Mol. Phys.
36
, 1409 (1978).
K. Yamanouchi, M.
Okunishi
, Y. Endo, S. Tsuchiya,
J. Mol.
Struct
.
352/353
, 541 (1995).
K.-E. J.
Hallin
, Ph.D. Thesis, University of British Columbia, 1977.Slide3
Low-Lying
V
ibrational Levels of C̃-State SO2(0,0,v3)(0,1,v3)
(0,2,
v
3
)
(0,3,
v
3
)
(1,0,v3)
v3 = 0
2
4
6
0
2
4
0
0
0
2
2
2
(v1, v2,v3) =
Tvib
— a1 levels
— b2 levels
(predicted)Slide4
Low-Lying
V
ibrational Levels of C̃-State SO2(0,0,v3)(0,1,v3
)
(0,2,
v
3
)
(0,3,
v
3
)(1,0,v3
)v3
= 0
12
3
4
5
6
0
1
2
3
4
0
001
1
22
21
(v1,
v
2
,
v
3
) =
T
vib
—
a
1
levels
—
b
2
levels
(predicted)Slide5
Decrease in n3
frequency
(
=1362
for
1
A
1
)
Consequence of a double-well minimum along
n
3
v
3
= 0
1
2
3
4
5
n
3
staggeringSlide6
Level Staggering as a function of n2
Slide7
A change of barrier height as a function of the bend angleSlide8
The Origins of the Unequal S-OElectronic configuration arguments by Mulliken
Vibronic
Coupling model by Innes:
1A
1
: (1a
2
)
2
(8a
1)2(3b1
)0
1B2
: (1a2)
1(8a1)2
(3b1)1
With a belief that the distortion of the
1B
2 state PES is too big to be accounted for by the pure electronic factor alone.
1A
1 ν3 = 1362 cm
-1
1B2 ν
3 = 212 cm-1 Slide9
q3-mediated Vibronic
Coupling modelA1B
2
Diabats
Adiabats
Interaction between the A
1
and
B
2
electronic
states is zero at
q3
Interaction can be turned on as the molecule moves along the q
3 direction (B
2 symmetry)Slide10
Diabats
Adiabats
Interaction between the A
1
and
B
2
electronic
states is zero at q3Interaction
can be turned on as the molecule moves along the q3
direction (B2
symmetry)
A1
B2
q
3
-mediated Vibronic
Coupling model
Zoomed-in
view to
reveal the
double-well minimumSlide11
Vibronic
Coupling in the
Diabatic BasisA1
B
2
Diabats
Selection rule:
v
3,A
=
v
3,B
± 1Slide12
The origins of the unequal S-O bond-lengths
Diabats
Adiabats
A
1
B
2
Diabats
D
AB
,
λ
AB
ω
3,B
ω
3,A
Fix D
AB
to the ab initio values (14760 cm
-1
)
Fix ω3,B to the ground state value (1362 cm
-1)Float
ω3,A and
λAB Slide13
Without constraints, rms
<2 cm
-1Is this physical?Slide14
Without constraints, rms
<2 cm
-1
Is this physical?
Definitely!Slide15
The increase in the level staggering as a function of
v
2 (bend) suggests that the effective barrier height of the double-well changes as a function of the bending angle.n3 staggering:
the approach to conical intersection
Theory predicts a seam of conical intersection between 1
1
B
2
and 2
1
A
1 at large bend angle (145-150°)Slide16
ConclusionsVibronic or Electronic?
The
vibronic coupling model is able to reproduce the observed staggered energy level pattern of the C̃1B2 state of SO2. It explains the change of effective barrier height as a function of the bend.Electronic interactions between high-lying electronic states (which have not been observed) are also qualitatively captured by the vibronic coupling model (i.e. low value of the effect ω3 in 21A1).Low-lying vibrational structure
gives information of interactions among higher-lying PES’s.
Park
et al. JCP 144, 144313 (2016)Slide17
AcknowledgementsTimothy James BarnumAlex HullDavid Grimes
Clare Keenan
Steve CoyJohn MuenterTrevor EricksonZhenhui Du